<html>
    <head>
        <title>
            HTML Course
        </title>
        <style>
            .f12 {
                font-size: 12px;
            };
        </style>
    </head>
    <body>
        <!-- <h1 id="instance1">
            Pragram1
            Paragrm2
        </h1>
        <h1 id="instance2" style="font-size: 12px;">
            Pragram1
            Paragrm2
        </h1>
        <a href="https://www.baidu.com/" target="_blank">百度</a> -->
        <h1>H1</h1>
        <h2>H2</h2>
        <h3>H3</h3>
        <hr>
        <h6>H6</h6>
        <hr>
        <a href="#table1">内部调整测试</a>
        <form action="demo_form.php" method="get">
            First name: <input type="text" name="fname"><br>
            Last name: <input type="text" name="lname"><br>
            <input type="submit" value="提交">
        </form>
        <iframe src="https://www.runoob.com/tags/tag-form.html" style="height: 700px;" frameborder="0"></iframe>

        <ul>
            <li>Coffee</li>
            <li>Tea</li>
            <li>Milk</li>
        </ul>
        <table border="1" id="table1">
            <tr>
                <th>名称</th>
                <th>年龄</th>
            </tr>
            <tr>    
                <td>张三</td>
                <td>23岁</td>
            </tr>
            <tr>    
                <td>张三</td>
                <td>23岁</td>
            </tr>
            <tr>    
                <td>张三</td>
                <td>23岁</td>
            </tr>
        </table>

        <div>
            div h1
        </div>
        <div>
            div h1
        </div>

        <span>
            sp1
        </span>
        <span>
            sp2
        </span>
        <script>
            var h1=document.getElementsByTagName("h1")[0]
            h1.innerText='edit1'
        </script>
    </body>
</html>